One hears about buried aircraft from time to time. If the aircraft were boxed and brand new, digging them up and rebuilding them to fly is a possibility. However, an aircraft buried as is would suffer the usual natural rigours. Aluminium alloys and magnesium bits would have suffered greatly. I have seen aircraft that were parked on prairies in Canada for "only" 30 years and they were bad enough (mind you, one and then another of this particular type has since flown).
Remember the P38 recovered from Greenland (one due to fly very soon)? They were new when they were force landed but were a bit bent when recovered.
However, where there is a will...